Twist grip shift lever for bicycles

ABSTRACT

A twist-grip shift mechanism that includes a housing part, a rotating part and a ring disposed in the rotating part. The housing part includes a cylindrical extension and a housing extension. The rotating part is rotatably mounted on the cylindrical extension. The cylindrical extension has tongues with retaining profiles extending from one end of the cylindrical extension for releaseably connecting to the ring. The tongues and the retaining profiles do not extend beyond an outer diameter of the cylindrical extension so that the housing part may be formed by an injection molding process using a single half of an injection mold, thereby eliminating undercuts and other molding inaccuracies.

BACKGROUND OF THE INVENTION

The invention relates to a twist-grip shift mechanism for bicycles andin particular a twist-grip shift mechanism having a housing part formedby an injection molding process using a single half of an injection moldto eliminate undercuts.

German Patent Application DE 197 23 346.5 discloses a shift mechanismfor controlling transmissions on bicycles, in particular a twist-gripshift mechanism to be fitted on the handlebars. This shift mechanismincludes a fixed housing connected to the handlebars and a housing thatis fixed axially with the fixed housing and can be rotated by hand. Thefixed housing and the rotatable housing form a unit. The rotatablehousing has an inner cylinder with outward-facing recesses and the fixedhousing has an outer cylinder with bayonet hooks on its axially outerend face. The inner cylinder of the rotatable housing may be pushed ontothe outer cylinder of the fixed housing to form a bearing. The twohousings may be connected permanently to one another by rotating therotatable housing relative to the fixed housing until a latching pointis reached.

A problem associated with the above configuration is the proper moldingof the two housing to form a satisfactory bearing. During the moldingprocess, undercuts may form. The undercuts cause parting seams andmolding inaccuracies which may cause connecting problems when the twohousings are bought together to form the bearing. Therefore, there is aneed for a shift mechanism that eliminates the above stated problem.

SUMMARY OF THE INVENTION

The present invention provides a twist-grip shift mechanism for bicycleswith a fixed housing which has a cylindrical extension surrounding ahandlebar to support a rotating part. To eliminate the above statedproblems the cylindrical extension is configured in such a way that nocontours that connect with the rotating part go beyond the outsidediameter of the cylindrical extension. Another factor that contributesto an efficient manufacturing process is that there is a housingextension surrounding a cable bobbin on the rotating part. The housingextension is formed as part of the housing part. The contours are formedon the outside diameter of the cylindrical extension during an injectionmolding method using a single mold half of an injection mold. Theadvantage of this manufacturing method is a homogeneous cylindricalsurface of the cylindrical extension, which serves as a bearing for therotating part resulting in no parting seams or molding inaccuracies thatcould impair operation of the twist-grip shift mechanism duringactuation.

The above-mentioned manufacturing method may also be used for moldingtongues with retaining profiles onto the cylindrical extension forreleasable assembly with latching profiles of a ring. The retainingprofiles include apertures to prevent them from projecting beyond thelimits determined by the inner and outer diameters of the cylindricalextension. The latching profiles on the ring are designed as hooksengageable with the apertures in the tongues.

The rotating part and the cable bobbin may be encapsulated with a grippart made of rubber-elastic material. Such a configuration allows aradially inward-pointing lip to be molded on the grip that extendsbeyond the overall length of the rotating part on the side opposite thecable bobbin. In the installed condition, the lip engages in a radiallyoutward-facing groove arranged in the ring. This allows the bearingbetween the rotating part and the cylindrical extension to be kept freefrom penetrating dirt, thus ensuring the functioning of the lubricatedbearing over a prolonged period.

It is therefore the object of the invention to provide an injectedmolded housing part for a twist-grip shift mechanism having acylindrical extension that includes an outer functional surface and ahousing extension that includes inner contours that is configured toallow the use of a single half of an injection mold, thereby eliminatingundercuts and other molding inaccuracies.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is an exploded view of a twist-grip shift mechanism in accordancewith a specific embodiment of the present invention;

FIG. 2 is an exploded view of a twist-grip shift mechanism in accordancewith a specific embodiment of the present invention;

FIG. 3 is a cross-sectional view of the twist-grip shift mechanism shownin FIG. 1; and

FIG. 4 is a cross-sectional view of the twist-grip shift mechanism shownin FIG. 2.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate two embodiments of a twist-grip shift mechanismof the present invention. The twist-grip shift mechanism includes ahousing part 1,1 a fixed on a handlebar tube of handlebars of a bicycle.The housing part 1,1 a may be configured in such a way that a tensioncable (not shown) may be pulled and released to control a bicycletransmission. The tension cable is connected to a rotating part 3,3 a bya cable bobbin 4,4 a arranged on the latter and is set in motion byrotating the bobbin. The rotating part 3,3 a is mounted rotatably on acylindrical extension 2,2 a connected to the housing part 1,1 a. In anaxial direction away from the housing part 11 a, the cylindricalextension 2,2 a has tongues 9,9 a with retaining profiles 10,10 a thatcan be joined together with latching profiles 11,11 a of a ring 12,12 a.The rotating part 3,3 a is mounted to the housing part 1,1 a by pushingit over the tongues 9,9 a and onto the cylindrical extension 2,2 a ofthe housing part 1,1 a. Resulting in the rotating part 3,3 a being fixedaxially relative to the housing part 1,1 a and supported rotatably onthe cylindrical extension 2,2 a.

Referring to FIGS. 1 and 3, the ring 12 may be pushed over the tongues 9within the rotating part 3 until the latching profiles 11 of the ring 12fit together with the retaining profiles 10 of the tongues 9. Resultingin the tongues 9 being forced to bend radially inward during assembly.Once the latching profiles 11 are fitted together with the retainingprofiles 10 of the tongues 9, the rotating part 3 is fixed axiallyrelative to the ring 12 by an end face 17 and, in the other direction,is fixed axially relative to the housing part 1.

In reference to FIGS. 1 to 4, the smallest inside diameter 7,7 a of thecylindrical extension 2,2 a with its tongue 9,9 a corresponds to thediameter of the handlebar tube. The bearing for the rotating part 3,3 ahas an outside diameter 8,8 a which must not be exceeded by theintegrally formed tongues 9,9 a with their retaining profiles 10,10 a inorder to ensure that these parts can be produced with a single half ofan injection mold by a material injection method. However, efficientproduction of the housing part 1,1 a is only possible if inner contours6,6 a of a housing extension 5,5 a that is formed integrally on thehousing part 1,1 a and forms an annular space that essentially surroundsthe cable bobbin 4,4 a can likewise be formed by this half of theinjection mold. The contours 6,6 a are arranged in the housing extension5,5 a to guarantee the functioning of the two parts 1,1 a and 3,3 a. Toensure that the bearing on a functional surface of the cylindricalextension 2,2 a and the inner contours 6,6 a in the housing extension5,5 a can be produced economically and with optimum molding accuracy, itis necessary that the retaining profiles 10,10 a on the tongues 9,9 a donot project beyond the diameters 7,7 a and 8,8 a.

The rotating part 3,3 a has a grip part 13,13 a connected to a radiallyoutward-facing surface of the rotating part, which is made from arubber-elastic material to allow better operation by the hand of thebicycle rider. The grip part 13,13 a has a lip 14,14 a that projectsbeyond the axial length of the rotating parts 3,3 a. The lip 14,14 apoints radially inward and extends into a groove 15,15 a in the ring12,12 a, thereby providing a labyrinth-type seal against contaminationof the bearing from outside. The groove 15,15 a is formed by an outercollar 16,16 a at the end of the ring 12,12 a. The collar 16,16 aprotects the end face of the grip part 13,13 a, which is sensitive toshock loading. In reference to FIGS. 3 and 4 the lip 14,14 a is deformedelastically during the fitting of the ring 12,12 a in order to enter thegroove 15,15 a. FIGS. 3 and 4 likewise show the twist-grip shiftmechanism as an assembly in the form in which it can be pushed onto thehandlebar tube of the handlebars of the bicycle and fixed there by ascrewed or clip-type connection (not shown).

Referring to FIGS. 2 and 4, which show another embodiment of thetwist-grip shift mechanism, the twist-grip shift mechanism includes thehousing part 1 a having the cylindrical extension 2 a and the tongues 9a plus the twisting part 3 a and with the ring 12 a. While the retainingprofiles 10 of the twist-grip shift mechanism shown in FIGS. 1 and 3 aredesigned as apertures, the tongues 9 a shown in FIGS. 2 and 4 haveT-shaped retaining profiles 10 a that can interact with correspondinglyshaped latching profiles lla in the ring 12 a. The difference betweenthe assembly of the ring 12 with the tongues 9 and the assembly of thering 12 a with the tongues 9 a is that, after being latched in, theretaining profiles 10 a of the tongues 9 a can be disengaged from thelatching profiles 11 a by turning the ring 12 a. During this process,the tongues 9 a are deflected radially inward, and the ring 12 a can bepulled off axially, although this is only possible while the shiftmechanism is not mounted on the handlebar tube of the handlebars of thebicycle. It should be pointed out once again that the functional surfaceof the cylindrical extension 2 a with the outside diameter 8 a can bemolded with a single mold half and the T-shaped retaining profiles 10 ado not exceed the outside diameter 8 a.

What is claimed is:
 1. A twist-grip shift mechanism for bicycles formounting in a grip region of a handlebar, the twist-grip shift mechanismcomprising: a housing part fixed to the handlebar, the housing parthaving a cylindrical extension surrounding the handlebar and a housingextension having an inner contour; a rotating part having a cable bobbinand rotatably mounted on the cylindrical extension, the housingextension at least partially surrounding the cable bobbin; and a ringdisposed in the rotating part and connected to the cylindricalextension, the cylindrical extension having tongues extending from oneend, the tongues having retaining profiles for engaging the ring, thetongues and retaining profiles not extending beyond an outside diameterof the cylindrical extension to allow the housing part to be formed byan injection molding process using a single half of an injection mold.2. The twist-grip shift mechanism as claimed in claim 1, wherein thetongues have a limited spring travel in a radial direction.
 3. Thetwist-grip shift mechanism as claimed in claim 1, wherein the retainingprofiles are joined releaseably to latching profiles on the ring.
 4. Thetwist-grip shift mechanism as claimed in claim 1, wherein the retainingprofiles are apertures in the tongues.
 5. The twist-grip shift mechanismas claimed in claim 1, wherein the tongues have a configuration suchthat the tongues are connected to and/or released from the ring when thetwist-grip shift mechanism is not connected to the handlebar.
 6. Thetwist-grip shift mechanism as claimed in claim 3, wherein the latchingprofile is released from the retaining profile by turning the ringrelative to the cylindrical extension.
 7. The twist-grip shift mechanismas claimed in claim 1, wherein the rotating part is secured in an axialposition by the housing part at one end and an end face of the ring atthe other end.
 8. The twist-grip shift mechanism as claimed in claim 1,wherein the rotating part is surrounded by a grip part made from arubber-elastic material and rotationally fixed to the rotating part. 9.The twist-grip shift mechanism as claimed in claim 8, wherein the grippart is produced by encapsulating the rotating part, thereby connectingit permanently to the rotating part.
 10. The twist-grip shift mechanismas claimed in claim 1, wherein on a side opposite the cable bobbin, thegrip part has a lip extending beyond an overall length of the rotatingpart, pointing radially inward and projecting into an outward-facinggroove in the ring to form a labyrinth seal.
 11. The twist-grip shiftmechanism as claimed in claim 10, wherein the groove of the ring isformed in a collar substantially covering an end of the grip part. 12.The twist-grip shift mechanism as claimed in claim 1, wherein theoutside diameter of the cylindrical extension is designed as ahomogeneous bearing for the rotating part without parting seams andmolding inaccuracies.
 13. The twist-grip shift mechanism as claimed inclaim 1, wherein the retaining profiles are T-shaped engageable withcorrespondingly shaped latching profiles on the ring.
 14. The twist-gripshift mechanism as claimed in claim 3, wherein the latching profiles onthe ring are hooks.